This a red flag?

Hi everyone...just wondering. I was talking to an old friend of mine who I haven't seen in over 20 years. We reconnected over FB. I take it that he's interested in me and would like to meet, see if there's chemistry. Me, I want to enjoy my summer and heal, and maybe if something good comes along, I'll see about it. I'm pretty much over the exN and there hasn't been any contact.

Anyway I was having a conversation with the old friend and my exN came up. We were talking about different people in my town and I was asking him about his youngest brother who I had never met. He was telling me who his youngest brother hung out with back in the day and he asked me did I know such and such (who is my ExN). I told him, yeah, that was my ex. Well he continues to tell me that if him and I were to ever get serious, he would inform my exN cause they are cool, out of respect for me and out of respect for him. I'm like what??????? Why????? My exN doesn't even deserve to know anything about me or my life or who I'm dating. I told the old friend that my exN is still married so why would he deserve to know anything about me? Now my old friend said he doesn't know the details of my ex relationship, but him just saying that tripped me out!

Am I just going crazy? Is this a red flag? I just feel like my gut instincts, are off track after missing or excusing the red flags with my exN.